Mapudungun (also called Mapuche or Araucanian) is the language of the Mapuche people and is usually treated as a language isolate, with no conclusively demonstrated relationship to other linguistic families. Some scholars have proposed links to families such as Andean, but none of these hypotheses is generally accepted. It has been spoken in south-central Chile and adjacent parts of Argentina since pre-Columbian times.

The Mapuche are the largest Indigenous people of Chile and also have a significant presence in southwestern Argentina, centered on the historic Araucanía region. Estimates of the number of speakers vary widely, generally falling in the range of several hundred thousand, though many people of Mapuche descent no longer speak the language fluently. Mapuche culture preserves traditional institutions such as the machi (a spiritual and healing authority) and ceremonies such as the nguillatún.

After the arrival of the Spanish in the sixteenth century, the Mapuche mounted a prolonged resistance that prevented the full conquest of their lands south of the Biobío River for centuries. Missionaries such as the Jesuit Luis de Valdivia documented the language early on, and Valdivia's grammar was published in 1606, one of the first records of the tongue. The frontier maintained relative Mapuche autonomy until the forced incorporation of Araucanía into the Chilean state in the nineteenth century.

Mapudungun is classified as an endangered language, since intergenerational transmission has weakened, especially in urban contexts. In recent decades, revitalization efforts have emerged, including intercultural bilingual education in Chilean and Argentine schools, media, and literary production in the language. There is ongoing debate over its official recognition, and some municipalities and local regulations have advanced its status, though at the national level its standing remains limited.